1. Field of the Invention
This invention concerns a heating iron utilizing the combustion heat of a liquefied gas and, more specifically, it relates to a heating iron using a liquefied gas and capable of providing flameless and complete catalytic combustion.
2. Description of the Prior Art
Heating irons using liquefied gas as a heat source and utilizing a combustion catalyst for the aid of flameless complete combustion have been proposed, for example, as disclosed in Japanese Patent Publication Nos. 6033/1970 and 29789/1970.
In the conventional heating irons of this type, a gas mixture of air and fuel gas (liquefied gas) is introduced to a combustion chamber, where it is completely burnt by the aid of an oxidizing reaction with a combustion catalyst. In this case, the gas mixture is at first ignited and burnt upstream of the combustion chamber by using gas lighter or the like other ignition means (pre-combustion), and the heat obtained therefrom is used to heat the combustion catalyst to a temperature sufficiently high to start the catalytic oxidizing reaction. Then, the exhaust from the pre-combustion containing still combustible components is subjected to flameless complete catalytic combustion in the combustion chamber.
In this system, however, since a portion of the gas mixture has already been burnt in pre-combustion upstream of the combustion chamber, combustion heat energy is wholly it available at the iron tip but it is partially dissipated wastefully to the surrounding portion of the tool.
Moreover, gas flame resulted from the pre-combustion (not catalytic but ordinary combustion) provides a danger of fire accidents. As is well-known, if an exposed flame is present, it will readily ignite vapors of burnable organic solvents, etc which are often used in the production lines of a electronics or other factories.
In view of the above, use of gas heating iron is severely inhibited in most factories and they are obliged to use electrical heating irons. However, the electrical heating iron presents other drawbacks of current leak or electrostatic induction which are, particularly, to sensitive electronic elements as described in our copending U.S. patent application Ser. No. 620,326, now U.S. Pat. No. 4,552,124.
The present inventor has already proposed an improved gas heating iron in the above-cited U.S. Patent application, in which flaming pre-combustion takes place only at the beginning stage, then the gas supply is interrupted and the flame is extinguished soon after the catalyst has been heated to a temperature at which the oxidizing catalytic reaction can be started, by the use of a shutter mechanism.
Subsequently, when the gas mixture is supplied again, flameless complete combustion can be started and continued with the catalyst already heated to the high temperature. This can substantially overcome the foregoing defects and our proposed heating irons have now been successfully employed by many users.
However, the present inventor, et al have still continued to develop a more improved gas heating iron, because the use of the shutter mechanism complicates the structure, unskilled workers may feel it troublesome to handle the shutter or the like and, in particular, because we intend to attain quite flameless combustion even at the ignition stage so that the heating iron can be used with no fire danger at all.